Can't acces preview mode!


Hello, I am a beginner in programming and some tutorials show how to use “express library” but when I try to load it on my own Preview Platform it doesn’t work…I’ve done some research and it said the port it’s the problem and I should use 8080 port but I am using the port , still doesn’t load…

The code I am trying to preview:

   var express = require("express");
   var app = express();
   app.get("/", function(req, res){
       res.send("Hi there");
   app.listen(process.env.PORT, process.env.IP, function(){
      console.log("server has started");